<mat-card *ngFor="let group of keys(groups)">
  <mat-card-header>
    <mat-card-title>{{ group }}</mat-card-title>
  </mat-card-header>
  <mat-card-content>
    <section *ngFor="let section of groups[group]" class="section">
      <a *ngFor="let helix of keys(section)"
        mat-button
        [routerLink]="['/', group + '.' + helix]">
        <mat-icon>group_work</mat-icon>
        {{ helix }}
      </a>
    </section>
  </mat-card-content>
</mat-card>
